U.S. patent application number 09/749195 was filed with the patent office on 2002-06-27 for adaptive protection for recloser control.
Invention is credited to Egolf, William M., Hart, David G., LaPlace, Carl J., McClure, Graeme N., McElray, Jeffrey L. SR..
Application Number | 20020080540 09/749195 |
Document ID | / |
Family ID | 25012677 |
Filed Date | 2002-06-27 |
United States Patent
Application |
20020080540 |
Kind Code |
A1 |
McElray, Jeffrey L. SR. ; et
al. |
June 27, 2002 |
Adaptive protection for recloser control
Abstract
A recloser is adaptively controlled so that it will operate in a
manner responsive to prevailing conditions such as time of day, day
of week, and/or load current. A protection setting group is stored
in a memory accessible by the recloser controller, and contains a
set of instructions for controlling the recloser based on the
prevailing conditions. The prevailing conditions are continuously
monitored, and the control of the recloser is based on the
prevailing conditions and the protection setting group.
Inventors: |
McElray, Jeffrey L. SR.;
(Wendell, NC) ; LaPlace, Carl J.; (Raleigh,
NC) ; Hart, David G.; (Raleigh, NC) ; Egolf,
William M.; (Apex, NC) ; McClure, Graeme N.;
(Highett Victoria, AU) |
Correspondence
Address: |
Steven B. Samuels, Esq.
WOODCOCK WASHBURN KURTZ
MACKIEWICZ & NORRIS LLP
One Liberty Place -46th Floor
Philadelphia
PA
19103
US
|
Family ID: |
25012677 |
Appl. No.: |
09/749195 |
Filed: |
December 27, 2000 |
Current U.S.
Class: |
361/59 |
Current CPC
Class: |
H02H 3/006 20130101;
H02H 3/06 20130101 |
Class at
Publication: |
361/59 |
International
Class: |
H02H 003/00 |
Claims
What is claimed:
1. A method for controlling a recloser for an electrical power
line, comprising: determining a protection setting group, the
protection setting group having at least one associated feature;
determining a present condition of the at least one associated
feature; determining a behavior function for the recloser based on
the protection setting group and the present condition; and
implementing the behavior function for the recloser, thereby
controlling the recloser responsive to the behavior function.
2. The method according to claim 1, further comprising continuously
monitoring the present condition and changing the behavior function
responsive to the monitoring.
3. The method according to claim 2, wherein the monitoring the
present condition comprises monitoring at predetermined
intervals.
4. The method according to claim 1, wherein the at least one
associated feature comprises one of time of day, day of week, and
month of year.
5. The method according to claim 1, wherein the at least one
associated feature comprises load current.
6. The method according to claim 1, wherein the behavior function
comprises one of fuse saving mode and fuse clearing mode.
7. The method according to claim 1, wherein the behavior function
comprises one of single-phase operation and three-phase
operation.
8. A recloser control system for an electrical power line,
comprising: a recloser; a memory comprising a protection setting
group having at least one behavior function with an associated
feature; and a recloser controller coupled to the recloser and the
memory for controlling the recloser responsive to one of the at
least one behavior functions in the protection setting group.
9. The recloser control system according to claim 8, wherein the
recloser controller monitors a present condition of each associated
feature of each behavior function in the protection setting group,
and determines the behavior function based on the present
condition.
10. The recloser control system according to claim 8, wherein the
recloser controller comprises the memory.
11. The recloser control system according to claim 8, wherein the
one associated feature comprises one of time of day, day of week,
and month of year.
12. The recloser control system according to claim 8, wherein the
associated feature comprises load current.
13. The recloser control system according to claim 8, wherein the
at least one behavior function comprises one of fuse saving mode
and fuse clearing mode.
14. The recloser control system according to claim 8, wherein the
at least one behavior function comprises one of single-phase
operation and three-phase operation.
15. A computer-readable medium having computer-executable
instructions for performing steps comprising: determining a
protection setting group for a recloser operating on an electrical
power line, the protection setting group having at least one
associated feature; determining a present condition of the at least
one associated feature; determining a behavior function for the
recloser based on the protection setting group and the present
condition; and implementing the behavior function for the recloser,
thereby controlling the recloser responsive to the behavior
function.
16. The computer-readable medium according to claim 15, further
comprising computer-executable instructions for continuously
monitoring the present condition and changing the behavior function
responsive to the monitoring.
17. The computer-readable medium according to claim 16, wherein
monitoring the present condition comprises monitoring at
predetermined intervals.
18. The computer-readable medium according to claim 15, wherein the
at least one associated feature comprises one of time of day, day
of week, month of year, and load current.
19. The computer-readable medium according to claim 15, wherein the
behavior function comprises one of fuse saving mode and fuse
clearing mode.
20. The computer-readable medium according to claim 15, wherein the
behavior function comprises one of single-phase operation and
three-phase operation.
Description
FIELD OF THE INVENTION
[0001] The present invention relates in general to the field of
electrical power distribution systems. More particularly, the
present invention relates to reclosers.
BACKGROUND OF THE INVENTION
[0002] A common problem in almost any electrical power distribution
system is a momentary disruption of electrical service, such as
might be caused by a momentary short circuit. For example, power
lines strung between poles could swing under wind loading,
momentarily touching each other or a grounded conductor. Things may
fall across exposed wires, arcing could occur, or other transitory
events could cause momentary power line short circuits or current
surges that could burn out a fuse or trip a recloser. Most of these
faults are self-correcting and do not require permanent fuse or
recloser protection because they terminate quickly. If a fuse
should burn out or a recloser should trip, the power line would be
open and customers would be deprived of their electrical power.
Service calls to replace fuses or reset reclosers would then be
required, thus escalating the utility's costs.
[0003] A recloser is a fault-interrupting device used to sense
current, voltage, and/or frequency and isolate faulted portions of
distribution feeders. A recloser control device operates a
recloser, which can be an electronic controller. Reclosers are
inserted into power lines to protect a power distribution
system.
[0004] More particularly, reclosers are electromechanical devices,
similar to circuit breakers. Reclosers are distributed at one or
more locations along a power line, typically upline from a fuse.
When the recloser controller detects a fault condition, the
recloser will begin to timeout. In other words, the recloser
controller will initiate a trip to open the recloser if the fault
condition has not cleared itself during a fixed time interval,
where the time interval is a function of current. Then, after a
time delay, as the name suggests, the recloser will close, and if
the fault condition has been cleared, power service is restored.
If, however, the fault condition has not been cleared, the recloser
controller will again trip open the recloser after a second fixed
time interval. If, after a predetermined number of reclose
operations, the fault condition has not been cleared, the recloser
controller will permanently lockout the recloser (i.e., permanently
open the circuit). The circuit then remains open until the system
is repaired and/or the fault condition is eliminated.
[0005] Thus, one primary function of a recloser is to save fuses.
In general, this is done by sensing the peak value of the current
conducted and interrupting its flow by opening or tripping a
recloser before a fuse blows. After a time delay, the recloser
closes, thereby restoring power to the system where it remains
closed until the next fault is sensed.
[0006] The rate at which a fuse will blow and interrupt current is
a function of the thermal heating of the fusible element. The rate
of thermal heating is proportional to the power generated by the
fault and each fuse has a time current characteristic, which
describes the time interval required to interrupt the fault
current. The time interval is generally approximately inversely
proportional to the value of the root mean square of the fault
current. It is desirable to coordinate the recloser with the fuses
to be saved to insure that the recloser in fact interrupts
temporary fault currents before the fuses to be protected are
blown. This is generally done by approximating the root mean square
value of the fault current by sensing its peak value.
[0007] It must also be recognized that not all faults, which occur
on a power distribution line, are temporary, such as those caused
by a tree branch momentarily falling against the line. Some faults
are of a more permanent nature such as those caused by a storm
where the entire pole structure has fallen to the ground. As a
consequence, reclosers are built so that they will only trip a
limited number of times within a short duration before locking
open. Were this not done, a recloser would cycle until failure and
many of the fuses to be protected would blow anyway.
[0008] At some magnitude of fault current it is desirable to have
the recloser open immediately to protect the line rather than
following an inverse time current characteristic. At intermediate
levels it may be desirable from the power distribution standpoint
to allow the fault current to flow for a limited period to allow
the fault to burn itself open or blow the fuse. Many reclosers have
alternate inverse time current characteristics, which achieve this
goal. Typically, a recloser will allow two shots or trip operations
to follow a fast time current characteristic and two additional
shots along a somewhat slower time current characteristic before
locking open or out.
[0009] Conventional reclosers for three-phase systems open all
three phases at the same time upon detection of a fault on any one
phase. Other three-phase systems implement three single-phase
reclosers, one on each phase. In these systems, each single-phase
recloser is independently controlled. This is costly and does not
allow for the phases to be responsive to one another.
[0010] Thus, in a typical configuration, for a fault, the recloser
will open to clear the fault. Note that for any fault, e.g.
single-phase-to-ground faults, phase-to-phase faults,
phase-to-phase-to-ground faults, and three-phase faults, a typical
recloser will open all three phases. For distribution feeders,
opening all three phases for a single-phase fault will result in
more customers losing power than necessary. However, if an electric
utility were to employ traditional single-phase recloser protection
on their distribution system, it would be implemented with three
independent single-phase mechanical reclosers--one for each phase.
This provides a per phase approach to single-phase faults but if
there is an evolving fault, such as, for example, two or more
phases are faulted, then the tripping and subsequent reclosing is
always done single-phase. Totally independent single-phase
reclosers can also be involved in a race condition. For
phase-to-phase faults, if one phase was to operate more quickly
than the other does, the recloser may not correctly isolate the
second faulted phase.
[0011] The recloser controller provides the intelligence that
enables a recloser to sense overcurrent faults, select timing
operations, time the tripping and reclosing functions, and lockout.
The hydraulic unit--an integral part of the recloser is used in all
single-phase reclosers and has a smaller rating of three-phase
reclosers. The electronic controller is generally used in the
single-phase reclosers and in higher ratings of three-phase
reclosers. Such devices, however, should be appropriately
programmed to coordinate in a predefined manner to endure that the
power distribution systems respond to line faults in accordance
with expectations.
[0012] Generally, when automatic circuit reclosers are used in
conjunction with fuses, they are configured in a variety of modes.
For example, the recloser or reclosing breaker may be configured
for a fuse saving or fuse clearing mode. In the fuse saving mode,
the automatic recloser or reclosing breaker operates faster than a
fuse, trying to clear a momentary fault. If the fault is still
present, the automatic circuit recloser operates more slowly than
the fuse, enabling the fuse to blow and clear the fault. In the
fuse-clearing mode, the automatic recloser is set so that for a
fault beyond any fuse in series with the recloser, the fault shall
be cleared by the fuse without causing the recloser to operate.
[0013] There are microprocessor-based recloser controllers which
are capable of detecting fault conditions, and, in response,
capable of timing out a corresponding recloser. However, these
prior designs are not adaptive. Instead, fault detection in these
prior designs is a function of some absolute (i.e., a fixed)
preprogrammed current level, such that gradual changes in load
current due to normal, daily and/or seasonal fluctuations are not
taken into consideration. Therefore, service may be unnecessarily
interrupted when the current fluctuation does not pose a threat to
the system. Moreover, fault detection schemes based on an absolute
current level may not always detect remote faults (i.e., faults
that occur along a distal portion of a power line with respect to
the position of the recloser).
[0014] It is thus desirable to provide recloser control that can
overcome the problems of the prior art. In this way, an electric
utility can adaptively set a recloser to function in a certain
manner, such as fuse saving, fuse clearing, single-phase, or
three-phase, based on prevailing conditions, such as time of day,
day of week, month, or load current, for example.
SUMMARY OF THE INVENTION
[0015] The present invention is directed to recloser operation that
is responsive to a particular protection setting group. Depending
on the prevailing conditions, such as the time of day or the load
current, the recloser functions in a certain manner, such as
single-phase or in a fuse saving mode.
[0016] According to one embodiment within the scope of the present
invention, a method for controlling a recloser for an electrical
power line comprises determining a protection setting group, the
protection setting group having at least one associated feature;
determining a present condition of the at least one associated
feature; determining a behavior function for the recloser based on
the protection setting group and the present condition; and
implementing the behavior function for the recloser, thereby
controlling the recloser responsive to the behavior function.
[0017] According to aspects of the invention, the present condition
is continuously monitored, and the behavior function is changed
responsive to the monitoring. The monitoring can take place at
predetermined times or events, such as predetermined intervals of
time.
[0018] According to another embodiment within the scope of the
invention, a recloser control system for an electrical power line
comprises a recloser, a memory comprising a protection setting
group having at least one behavior function with an associated
feature, and a recloser controller coupled to the recloser and the
memory for controlling the recloser responsive to one of the at
least one behavior functions in the protection setting group.
[0019] The foregoing and other aspects of the present invention
will become apparent from the following detailed description of the
invention when considered in conjunction with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] FIG. 1 is a simplified schematic diagram of a system in
which the present invention may be embodied;
[0021] FIG. 2 is a simplified schematic diagram of an exemplary
protection setting group in accordance with the present
invention;
[0022] FIG. 3 is a simplified schematic diagram of another
exemplary protection setting group in accordance with the present
invention; and
[0023] FIG. 4 is a flow chart of an exemplary method of operation
in accordance with the present invention.
DESCRIPTION OF EXEMPLARY EMBODIMENTS AND BEST MODE
[0024] The present invention is directed to systems and methods for
adaptively controlling a recloser so that it will operate in a
manner responsive to prevailing conditions such as time or load
current.
[0025] Electrical transmission lines and power generation equipment
must be protected against insulation faults and consequent short
circuits, which could cause a collapse of the power system, serious
and expensive equipment damage, and personal injury. Further,
extensive power outages may cause angst among consumers that expect
reliable and trustworthy utility service. It is the function of the
fault protection devices such as fuses and protective relays to
assist in the isolation of line faults and initiate isolation by
tripping reclosers. In addition, power distribution operators
employ automatic power restoration components to automatically
bring power distribution systems back on-line in the event of a
protection fault or other system malfunction.
[0026] Automatic recloser devices are used in electrical
distribution systems to protect high voltage power lines. Such
devices are usually mounted to the poles or towers that suspend
power lines above the ground. However, use with below ground
systems is also known. The recloser device is used to minimize
power distribution interruptions caused by transients or
faults.
[0027] Typically, during a system disturbance, large increases in
current, i.e., faults, will occur. Sensing a current increase, the
recloser will open thereby cutting off current flow in order to
protect distribution system components and other equipment
connected to the distribution system. Since many fault conditions
are temporary, the recloser is designed to close after a short time
delay, thereby establishing normal current flow. For example,
during a thunderstorm, if lightning were to strike the distribution
system, the power to one's home may be disrupted for a few seconds
causing lights and appliances to turn OFF (recloser opening), then
ON (recloser closing). Once the recloser closes, if it senses the
continued presence of increased current, (e.g. fault current rather
than load current), it will again open. Such cycling between open
and closed may occur three times before the recloser remains
open.
[0028] When used in conjunction with other protection devices, such
as a fuse or protective relay, an automatic power restoration
device may operate in two modes, fuse saving or fuse clearing. In
the fuse saving mode, the automatic power restoration device
operates faster than a cooperating fuse, trying to clear a
momentary fault. In the event the fault is still present after the
restoration device's attempts to restore the system, the automatic
power restoration device operates more slowly than the fuse,
allowing the fuse to clear the fault. In the fuse clearing mode,
the automatic power restoration device is configured so that a
fault occurring beyond any fuse that is connected in series with
such fault is cleared by the fuse without causing the recloser to
operate.
[0029] A simplified schematic diagram of a system in which the
present invention may be embodied is shown in FIG. 1. A recloser 10
is a switch that opens and closes a power line 5 (e.g., between a
substation and a load), and which is operated by a recloser control
device 20 such as an electronic controller. It should be understood
that the term "recloser" covers various combinations of reclosers,
sectionalizers, circuit breakers and the like, which may also be
used within the scope of this invention. The power line 5 is a
three-phase power line. The recloser 10 comprises three poles 15.
Each pole 15 is connected to an associated wire on the power line
5, thereby being energized by an associated phase.
[0030] The basic components of an automatic recloser 10 are a
high-speed circuit breaker, overcurrent protection, trip logic, and
automatic closing logic with an operation counter. When an
overcurrent of sufficient magnitude (i.e., greater than a
predetermined amount of current) flows through the recloser 10, the
tripping action is initiated and a circuit interrupting contact
within the pole 15 opens with an operation counter advancing one
count. After a preset time delay, the recloser contacts are
automatically closed, thereby re-energizing the line 5. If the
fault persists, this tripping and reclosing sequence is repeated a
predetermined number of times, as set by the controller 20, until a
lockout function is initiated. If the fault was transient and
cleared during any period when the recloser 10 was open, then the
recloser 20 will remain closed after a short time delay reset to
its original condition ready for the next operation.
[0031] An exemplary recloser for use with the present invention is
the VR-3S recloser manufactured and distributed by ABB Power
T&D Company, Inc., Raleigh, N.C. Magnetic actuators open and
close the recloser's main contacts.
[0032] The recloser 10 is controlled by a microprocessor-based
controller 20 that contains software. There are two basic design
areas that make up a microprocessor-based controller 20. The
physical elements, such as integrated circuits, resistors,
capacitors, displays, switches, and so forth, are called
"hardware". Once constructed, they are not readily changeable. The
second basic design area in the microcomputer includes computer
programs and documentation. These elements are called "software"
since they are readily changeable.
[0033] A microcomputer based on a microprocessor and associated
memories and interfacing components is used in the recloser
controller 20 to process input signals in a manner appropriate for
recloser control. The microprocessor performs the various
arithmetic and logic functions of the control. In particular, the
required logic circuits as well as capabilities for servicing are
typically included.
[0034] A power supply is typically provided in a recloser control
system and provides power to other components of the control system
and includes power storage means to supply power when the protected
lines are interrupted. A secondary overcurrent trip circuit in the
control functions independently of the microcomputer when the
microcomputer is disabled to effect a trip operation of the
recloser. A protective input network protects the controllers low
power devices from the hostile environment of the power
distribution system and scaling means are used to allow the
microcomputer and associated circuitry to function with more
precision in the range of input signal magnitudes where precision
is desirable and to allow the control to function with a limited
number of components over a wide range of input signals.
[0035] Storage or memory 30 is provided for temporarily and/or
permanently storing data. In a recloser 10, for example, this data
would include line current magnitudes and command information such
as multiple time-current characteristic curves and protection
setting groups, as further described below. The memory can be
random access memory (RAM) or read only memory (ROM) or any other
type of memory. ROM is preferably electrically programmable for
easy modification and is used for storing programming information.
The storage 30 can be internal to the controller 20, as shown, or
be located external to the controller 20.
[0036] The front panel of a recloser controller 20 may include a
display for displaying information. A keyboard or other input
device may be used for entering information. Indicator lamps
provide status information such as recloser open, recloser closed,
control lock out, above minimum trip, malfunction and lock in.
[0037] Through the use of the switches and keyboard mentioned
above, the operations of the device can be controlled by command
information. Typical command information for a recloser controller
includes first time current characteristics for phase and ground
currents which usually result in the more rapid tripping of the
recloser 10, and second time current characteristics for phase and
ground currents which usually result in the recloser 10 remaining
closed longer under fault conditions. Other command information
includes minimum trip levels for phase and ground currents which in
a recloser controller begins the timing process in accordance with
the time current characteristic, number of shots to lock out under
phase and ground faults, and number of times which a given time
current characteristic will be followed. Further command
information may include a reset time interval which determines the
duration which a counter recording the shot number will retain that
information under non-fault conditions, and multiple reclose
intervals which determine the time that the recloser 10 will remain
open. Additional command information may include a high current
constant time feature which allows the recloser 10 to remain closed
only for a fixed duration under certain magnitudes of fault
currents. Thus, if there is a fault, the line 5 is opened for a
short period of time. At an end of a given time period following
the opening of the line 5, the recloser 10 closes the line 5. If
the abnormal condition persists, the recloser 10 again opens and
closes the line 5.
[0038] The command information in accordance with the present
invention can include a plurality of independent protection
settings groups. The protection setting group can be programmed by
a technician or by the customer, either when the system is on-line
or off-line. A protection setting group is an instruction set for
controlling a recloser based on certain conditions. An exemplary
protection setting group is shown in FIG. 2. Here, the protection
setting group is based on time of day and day of week. A
fuse-clearing mode is enabled for a particular time and day (e.g.,
during business hours, Monday through Friday) and a fuse saving
mode is enabled for the remaining times (e.g., during weekends and
after business hours). In this manner, the quality of supply is
optimized for a majority of customers during business hours, Monday
through Friday, and operating expenditures are minimized when the
quality of the supply is not as critical (during weekends and after
business hours).
[0039] Another exemplary protection setting group is shown in FIG.
3. Here, the recloser is set to operate in one phase (single-phase)
mode or three-phase mode depending on the month of the year.
Single-phase operation is implemented from October through March,
and three-phase operation is implemented from April through
September. In this manner, for example, in a rural area, irrigation
may take place for several months of the year, in which three-phase
protection is desired to adequately protect pump motors. During the
remaining months, it is desirable to have one phase protection
because active loads are single-phase in nature and it is desirable
to minimize the effects of outages due to faults. Thus, a clock and
calendar can be used to control the operation of the recloser as
single-phase or three-phase operation, and / or fuse clearing mode
or fuse saving mode.
[0040] Another exemplary protection setting group can be based on
the load current. Based on the load current, different features are
enabled, such as fuse saving or fuse clearing protection, and
single-phase or three-phase operation. In this manner, protection
can be established to behave differently to a given fault based on
which protection setting group is active, based on the prevailing
conditions.
[0041] It should be understood any of a number of microprocessors
could be used to the same effect described above. Each
manufacturer's family requires that the peculiarities of their
devices be satisfied and in the microcomputer portion of the
recloser controller 20, and it would be impossible to go into
sufficient detail to describe the functioning control and be
sufficiently general to adequately describe the use of alternative
devices. One skilled in the art could readily amplify and modify
the description given to make them applicable to the devices of
other manufacturers by reading the normal technical literature
provided by the manufacturer of another device. Moreover, it would
be extremely confusing to attempt to describe all the minor details
contained within the software and only the more general software
modules and programs are described since one skilled in the art
could readily flesh out the skeleton provided.
[0042] An exemplary control unit is the PCD2000 power control
device manufactured and distributed by ABB Power T&D Company,
Inc., Raleigh, N.C. The control device can provide an interface for
remote communication with SCADA systems using MODBUS RTU, MODBUS
ASCII, and DNP 3.0 protocols. The controller can be programmed to
implement other protocols. Ports are available for external links
through a radio, modem, or direct fiber optic communications, for
example.
[0043] FIG. 4 is a flow chart of an exemplary method of operation
in accordance with the present invention. During power delivery,
the recloser 10 monitors the power line 5. At step 100, the setting
group is determined, selected, or otherwise set. The setting group
can be retrieved from a storage area 30 (e.g., a memory within, or
coupled to, the recloser controller 20). A plurality of setting
groups (related or unrelated) can be stored in the storage area 30,
and a technician or customer can choose the desired setting group
while the system is on-line or off-line.
[0044] After the setting group has been determined, the present or
prevailing conditions of the features associated with the setting
group are determined at step 110. For example, if the setting group
of FIG. 2 is active, the time of day and day of the week would be
determined, because the fuse clearing or fuse saving mode is set
dependent on these two parameters. As another example, if the
setting group of FIG. 3 is active, the month of the year is
determined, because single-phase or three-phase operation is set
responsive to the month of the year.
[0045] At step 120, the appropriate recloser behavior is determined
from the protection setting group based on the prevailing
conditions. This is performed by comparing the prevailing
conditions step 110 to the conditional entries in the protection
setting group step 100, and the entry that matches is implemented,
at step 130. Thus, for example, if the setting group of FIG. 2 is
active, and it is 1:00 pm on a Wednesday, then based on the
protection setting group entries, the fuse clearing mode is
implemented.
[0046] The present or prevailing conditions are continuously
monitored, at step 140, to determine if the recloser behavior
should be changed, as determined at step 150. If the behavior
should change, the new behavior is determined and implemented with
processing continuing at step 130. If the behavior should not
change, the conditions are monitored, with processing continuing at
step 140. The prevailing conditions are monitored at predetermined
intervals (of time, for example) or at other events, which can be
programmed by a technician or customer.
[0047] Thus, for example, if the setting group of FIG. 2 is active,
when the time changes from 5:00 pm to 5:01 pm, on a Wednesday, the
mode changes from fuse clearing to fuse saving. The fuse saving
mode is implemented until 8:00 am on Thursday, at which time the
mode changes to fuse clearing.
[0048] The invention may be embodied in the form of appropriate
computer software or in the form of appropriate hardware or a
combination of appropriate hardware and software without departing
from the spirit and scope of the present invention. Further details
regarding such hardware and/or software should be apparent to the
relevant general public. Accordingly, further descriptions of such
hardware and/or software herein are not believed to be
necessary.
[0049] Although illustrated and described herein with reference to
certain specific embodiments, the present invention is nevertheless
not intended to be limited to the details shown. Rather, various
modifications may be made in the details within the scope and range
of equivalents of the claims and without departing from the
invention.
* * * * *